Symfony events without statics

experiment.php

<?php

namespace MeadSteve\Eventing;

require_once "vendor/autoload.php";

use Symfony\Component\EventDispatcher\EventDispatcher as SymfonyEventDispatcher;
use Symfony\Component\EventDispatcher\EventDispatcherInterface;
use \Symfony\Component\EventDispatcher\Event;

interface ObjectListenerInterface
{
    public function addListeners(EventDispatcherInterface $dispatcher);
    public function removeListeners(EventDispatcherInterface $dispatcher);
}

class EventDispatcher extends SymfonyEventDispatcher
{
    public function addObjectListener(ObjectListenerInterface $subscriber)
    {
        $subscriber->addListeners($this);
    }

    public function removeObjectListener(ObjectListenerInterface $subscriber)
    {
        $subscriber->removeListeners($this);
    }
}

class MessageEvent extends Event
{
    protected $message;

    public function __construct($message)
    {
        $this->message = $message;
    }

    public function getMessage()
    {
        return $this->message;
    }
}

class Subscriber implements ObjectListenerInterface
{
    public function addListeners(EventDispatcherInterface $dispatcher)
    {
        $dispatcher->addListener("say.message", array($this, "say"));
    }

    public function removeListeners(EventDispatcherInterface $dispatcher)
    {
        $dispatcher->removeListener("say.message", array($this, "say"));
    }

    public function say(Event $event)
    {
        if ($event instanceof MessageEvent) {
            echo $event->getMessage();
        }
    }

}

$dispatcher = new EventDispatcher();
$subscriber = new Subscriber();

$dispatcher->addObjectListener($subscriber);
$dispatcher->dispatch("say.message", new MessageEvent("hello"));

$dispatcher->removeObjectListener($subscriber);
$dispatcher->dispatch("say.message", new MessageEvent("I should not be said by subscriber"));